1. Field of the Invention
The present invention relates to the material removing machining of wafer shaped workpieces, in particular semiconductor wafers. The present invention also relates to a method for achieving a wear performance which is as linear as possible for a tool which has an essentially planar working surface for the material removing machining of wafer shaped workpieces, and relates to a tool having a wear performance which is as linear as possible. The present invention also relates to a method and a device for measuring a wear profile on an essentially planar working surface for the material removing machining of wafer shaped workpieces. Finally, the present invention also relates to a carrier which is used for the two-sided material removing machining of wafer shaped workpieces.
2. The Prior Art
Prior art known carriers are described in U.S. Pat. No. 4,739,589.
Wafer shaped workpieces can be subjected to a material removing machining in various ways. As a rule, the machining has one or more of the following objectives. For example, removing damage close to the surface is an objective, plus an increase in planarity and parallelism of the wafer sides is another objective as well as smoothing the wafer sides. The machine tools are usually grinding, lapping and polishing tools. A common feature of the tools is an essentially planar working surface which can be used to machine one side of the workpiece. During the machining of the workpiece, the workpiece and the working surface of the machine tool execute a relative movement. With regard to the number of workpieces which are machined simultaneously, it is possible to distinguish between single wafer machining and batch machining. It is also possible to make a distinction with regard to the number of sides of the wafers machined, the distinction being between single side machining and double side machining. The present invention can in principle be applied to all the abovementioned machining processes.
Wear to the working surface of the machine tool is practically always associated with the material removing machining of a workpiece. Over the course of time, this wear means that it is no longer possible to machine the workpiece uniformly, so that the shape of the machined workpieces becomes incorrect. For this reason, the working surface of the tool has to be corrected at regular intervals, for example by regrinding or by leveling using trimming rings. However, frequent interruptions to work caused by correction intervals impair the productivity of the machining process considerably.